#define _CRT_SECURE_NO_WARNINGS 1
class Solution {
public:
    bool containsDuplicate(vector<int>& nums) {
        unordered_map<int, int> hash;
        for (auto e : nums)
        {
            if (hash.count(e))
            {
                return true;
            }
            hash[e]++;
        }
        return false;
    }
};